First, unless it broke, you will need to
open the staple and remove the old belt. Please, DO NOT use a screwdriver to
open the staple. This is an invitation to a whole new concept in body piercing!
Use two pairs of pliers.

New treadle belts come too long, and with
a metal staple on one end. Feed it on (If you can, carefully observe how the
old one fed) and pull the two ends along side each other until the belt is just
barely snug. Mark the correct length and cut it off there. (Just thought I'd
mention it... don't cut the end with the staple!) Use an ice pick and a block
of wood and poke a hole in the cut end to accept the open end of the staple.
Put the staple through the hole, roll the belt onto the wheel and try the action.
(It is helpful if you don't bend the staple closed for this trial. You may be
trying it several times and if you repeatedly open and close the staple, it
may break off. Bend it closed when you have achieved a good length.) At this
point, the belt may well be too loose, which is way better than too tight. From
this point, repeat the process, only with each attempt, cut the end off exactly
at the staple hole (which should be about 1/4" in from the end.). You will be
surprised at how much difference that tiny adjustment can make.

Anyhow, when the belt turns the
machine smoothly and easily, stop. In a week or two of use, the belt may well
stretch and you will have to make another fitting adjustment. The key thing
is not to get it too tight. It will cause the machine to be sluggish and your
foot to get tired. The treadling should be easy and the belt just tight enough
to sew, but not to slip. Another little trick... Lots of times old belts get
greasy and leave the treadle wheel and hand wheel grooves greasy. Take a rag
with alcohol or gasoline on it and clean the grooves
by holding the rag down into them while you turn the wheels. When they are nice
and clean, dry them. When oiling the machine, try to keep oil out of the grooves
and off of the belt. Here is still another trick… go to a music store and buy
a violinist's rosin block. These are used to rosin the violin bow. Leave the
belt on your treadle a little looser than you probably think it should be. Release
the clutch on the hand wheel, as if you were going to wind a bobbin. Pump the
machine real fast, and hold the rosin block against the back of the belt. It
will pick up some rosin and that will give it a better "grip" on the hand wheel
and drive wheel. Using the rosin lets you work with a bit looser belt, which
in turn makes the treadling easier.

One of our
members sent in this tip, which may also be helpful:

"I just read "how
to install a new belt" and wanted to add a tip.. My
friend, who used to repair machines for a living, put my new belt behind
his shoulders and stretched it before he put it on the machine, He
said, by doing that, it would be a longer period of time before I had to
adjust the initial stretch that always happens right after putting a new
belt on a machine. It makes sense...
Anita "

Removing the Treadle Belt to Lower the
Machine

If you look at the drive wheel on your treadle,
you should see a notch in it. Usually, unless it has been removed, there is
also a little lever with a kind or loop or ring on it that moves. The treadle
belt goes
through that loop as part of the installation. When you want to release the
tension on the belt, you either pull the lever on the loop, which causes it
to press the belt to the outside, or if the loop isn't there, you gently press
the belt to the outside with your hand. Then turn the wheel slowly, using either
the pedal or the handwheel. The drive wheel will rotate, the belt will catch
in the notch in the wheel, and as the wheel turn, it will pull the belt out
of the groove, releasing the tension. You then can lower the machine with no
trouble. When you want to sew again, raise the machine, make sure the belt is
in the groove of the hand wheel, then turn the drive wheel until you can see
the notch. Catch the belt in the notch, turn the drive wheel and the wheel will
pull the belt back into the groove. Study the situation and try it a few times.

Operating a treadle takes a little getting
used to . But there is a right way. These machines have big hand-wheels because
your hand is used to get it going and because the extra weight makes treadling
easier. First, place your right foot or both feet on the (full surface) of the
treadle platform. Make sure your sewing is all set. Now, lightly touch the hand-wheel
and start rotating it toward you. (NOTE: Most machines operate with the top
of the hand-wheel moving toward you… some, notably White and Wheeler and Wilson,
are the reverse. If you are not getting a stitch, try going in the opposite
direction.) Let your feet do what the treadle wants to do at first, then start
using your feet to take over and control the movement at whatever speed you
are comfortable with. You can use your hand to brake or slow down and stop the
machine's motion. As you gain rhythm, try not to let the wheel turn backwards,
this will break the stitching. Also, as you use the machine, your will develop
the ability to be aware of the handwheel out of the corner of your eye, and
observe which way it wants to start so easily that you can change it's direction
with just your feet.

When you take your feet off of the platform,
you will find the needle wants to move. The weight of the drive wheel rotates
to the bottom, causing the machine to make a stitch. Be sure to clear the treads
before you start a new seam or you will get a tangle.

Like anything else, treadling is a skill.
The more you do it, the better you'll learn it.